The present invention relates to a vacuum insulated switching apparatus provided with a vacuum pressure measuring device.
Switching performance and dielectric strength of a vacuum circuit switch is decreased rapidly when vacuum pressure is increased higher than 10.sup.-4 Torr. Reasons of varying the vacuum pressure include vacuum leakage by generating cracks, release of gaseous molecules adsorbed onto metals and insulating materials, penetration of atmospheric gases, and others. In view of the increasing size of the vacuum vessel in addition to the increasing voltage of the vacuum circuit switch, the release of the adsorbed gas as well as the penetration of atmospheric gas are no longer negligible. In accordance with a structure of the insulated switching apparatus as disclosed in JP-A-9-153320 (1997), wherein a breaker, a disconnector, and a ground switch are integrated in a single bulb, vessel, the addition of a vacuum pressure checking function during operation, or of a continuous pressure monitoring function is desirable, in order to ensure the safety of operators for maintenance and inspection of the load, or of the switching apparatus itself.
Conventionally, vacuum switches provided with vacuum pressure measuring apparatus such as one provided with an ionization vacuum gauge, one in which vacuum pressure is determined by applying a voltage to a small gap provided in the 5 vacuum vessel to cause discharge, one which is provided with a magnetron terminal, and others are known.